


Santa, Baby

by hovercraft



Category: Fate/Grand Order, Fate/stay night & Related Fandoms
Genre: Bondage, Jealousy, M/M, Pining, Sex Toys, no beta we die like men
Language: English
Status: Completed
Published: 2021-01-17
Updated: 2021-01-17
Packaged: 2021-03-14 21:48:23
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,753
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28802319
Author URL: https://archiveofourown.org/users/hovercraft/pseuds/hovercraft
Summary: Caster is a little jealous that Archer has an Arthur all to himself. Wishing he had one to tease on his own, he's surprised on Christmas Eve with a wish come true.(PWP, commission for @Basykail!)
Relationships: Gilgamesh | Archer/Arthur Pendragon | Saber
Comments: 7
Kudos: 27





	Santa, Baby

**Author's Note:**

  * For [Basykail](https://archiveofourown.org/users/Basykail/gifts).



It was his Archer self that showed him around the moment he was summoned into Chaldea.

Caster wasn’t impressed with much; Chaldea’s technology might have been leagues ahead of his own time’s, but it was inefficient. Why were servants eating in the cafeteria so often without a need to replenish mana? Why were servants… playing games in the rec room instead of farming? Sooner rather than later, he’d realize Chaldea was a place of comfort and bonds, and that was why these servants had such privileges— because Chaldea’s master loved them too much, and they were spoiled after years of Holy Grail wars. It was… irritating, to say the least, but he was sure once he was put to work, he’d get this place running smoothly.

Archer didn’t bother to introduce many servants, as Caster didn’t care to know them either, but there was one that caught his eye immediately. A knight in blue and silver armor, with a gentle expression on his face. For whatever reason, Caster was taken with him immediately.

“And who is that…?” Caster leaned over to Archer, clearly showing some interest.

“That is one servant you may never touch,” Archer said haughtily. “I’ve already claimed him as my own. Arthur Pendragon— from another universe.”

“Claimed him as your own…” Caster asked, suspiciously. “And he knows that?”

“He does. He’s been amenable to my courtship.”

“Hm.”

The disappointment was palpable in his voice, but it wasn’t so deep that it hurt. It was simply a missed opportunity. Of course, he and his younger self shared a preference, but he paused when he saw Arthur make his way over to the two of them. He was radiant… sure, and as he spoke, Caster noted the responsibility and regality in his voice. He was neither too humble, nor too abrasive and something about his voice was so enduringly charming that he couldn’t let it go.

“It’s an honor to meet you, Your Highness. I’m glad I get to see all sides of Gilgamesh’s self, including you.”

“Really?” Caster felt like testing him. “Are you really so taken with me that you’ll endear yourself to all parts of me?”

Arthur’s answer was as smooth as a response could get. “Everyone has different sides to themselves, myself included. I’ve grown… fond of Gilgamesh with all of our different adventures here in Chaldea.” ‘Fond’ clearly had some undertone not worth stating in public. “Not many people get to see people at different stages of their lives, seeing how they changed… I’ll accept you just as much as I’ll accept him.”

Caster was tempted to flirt a little more, but Archer was giving him that look of pride and possession that only allowed him to proceed at his own caution. He simply noted that Arthur was a charming man and he would keep note of him for future reference.

Maybe someday, there’d be another Arthur in Chaldea just as he’d appeared, who Caster could talk to.

—

Chaldea life would continue on as normal.

Caster was surprised to find himself somewhat envious.

Not entirely, not sincerely, but Arthur had his charm. Caster would earn his curiosity either way, despite Archer’s jealousy. There was something one couldn’t ignore about meeting your significant other’s older self that piqued curiosity. How had he changed, and what changed him? Arthur got a little subdued at mentions of Enkidu, wondering how he stacked up against his best friend, but Caster was tempted to tell him not to worry— Gilgamesh’s heart was as big as he was mighty, even if one person held the coveted top spot, he still had more than enough room for someone who was exactly his type.

But— that would be considered flirting, so Caster didn’t say it.

Instead, he buried himself into his work, occasionally being put on teams that best suited his strengths, and other times Ritsuka would curiously put him on a team with Archer and Arthur. It didn’t make sense to him, seemed woefully inefficient and a poor job of making him jealous— but he couldn’t deny what was right in front of him, either. Their flirting, Arthur’s charming demeanor… he was too old for such princely notions but if there was an “Arthur” that was his age, or at least a bit more mature, then he’d be interested— and Archer would have nothing to say about that.

Another Christmas would be coming soon. Archer started asking Caster for whatever the ‘best gift’ one could give someone like Arthur could be.

“Nothing in our treasury,” Caster said firmly. “He obviously doesn’t care for wealth.”

“I don’t suppose _I_ would make a perfect gift?”

Caster raised an eyebrow. “He already has you.”

“True… then I shall remind him of what a gift it is to _have_ me.”

This one’s ego… knew no bounds, but it wasn’t as if Caster could complain about his youth, having it built him up into the man he was today. Plus, he was getting a little annoyed with all this talk about Arthur. Just once, he wished he had someone else he could taunt and tease the way Gil did Arthur— and though that wish was insincere in some ways…

It was heard.

—

Night fell in Chaldea and Caster was forgoing sleep (as most Servants tried) to work. However, like it or not, his ether body was giving into exhaustion, and their master was likely long asleep. No mana from a command seal. Still, it made him feel _weak_ to be so exhausted, and usually, he fought that exhaustion to the brink of passing out. Not tonight. He could disappear into his spirit form to save mana, or he could try replenishing it the way humans do— through a short nap.

Nothing to lose.

He undid the heavy metal on his waist and sat aside his tablet, climbing into bed. He sighed, trying to get into the right mindset for sleep… whatever that was. It had been so long since he last tried that he might as well have never slept at all. Closing his eyes, he tried to will himself into unconsciousness— not to dream this Christmas Eve, but just to rest. To replenish what he had spent several times over.

Several times through the night, he heard the ring of bells. No doubt foolish servants in the hallway making merry and whatever they liked. For some reason, it made him especially bitter, something about the magic of the night just made him want to fall asleep faster.

But someone wouldn’t let him.

The door to his room slid open, bells ringing with every step.

“Mephistopheles, I swear—”

“Look at me. I’m no clown.”

Caster, fully prepared to give this person the ‘mongrel’ lay down for stirring him from a sleepless venture, was surprised to find Arthur standing in the doorway, dressed similarly— but not quite— to Santa himself. Cloaked in a blue hood, Gilgamesh could still see golden eyes beneath it. An Alter… still, Caster laughed, sitting up on his bed and deciding to lay out his problems to this Santa Claus with full fervor.

“Have you come to mock me? Don’t you have another Gilgamesh to be entertaining tonight?”

“Only one Gilgamesh had a wish strong enough to meet me,” Rider Arthur responded. “That would be you, wouldn’t it?”

“Don’t be ridiculous! I don’t care what you do or what my other self does with you, I—”

“Only a wish could make me appear like this,” Rider tilted his head, gently. “You want an Arthur for your very own, don’t you? Unfortunately, I don’t have that in my bag, but I do have… me.”

“Stop this incessant badgering, Mongrel, I don’t—”

Rider leaned in to kiss him, producing a sprig of mistletoe above their heads. His other hand cupped Gilgamesh’s chin, and to his surprise and dismay, it was exactly like he thought kissing Arthur would be. Wonderful, warm… the sweetest taste and the softest lips. Perhaps he had too many unbidden fantasies about the man that he didn’t want to come to light, but had it really manifested in this Arthur coming to life and coming to kiss him?

No matter. What was done, was done.

“Well, you’ve given me a kiss. Now it’s time for you to get to the other servants—”

“You’re mistaken. They have their own Santa. I’m here only for you.”

Gilgamesh paused at the insinuation, feeling himself grow more intrigued by the minute, knowing he could test Arthur for all he was worth and still see him walk out the door. “I don’t suppose you’re here to ravish me, hm? The door’s over there. I don’t want anything unless you’re willing to give it all.”

Without words, Arthur began to strip off his hood, then the blue tunic underneath. Gilgamesh would’ve been surprised, but he kept a calm demeanor to hide his ever-growing excitement. An Arthur just for _him_ — a Santa, sure, and he would only ever be here one night, but— how could he pass up a chance to work out his frustrations? His jealousy, as much as he wished he didn’t have it? Something his other self didn’t touch, something just for him, born from a wish.

“You’re making the mistake of thinking I need an Arthur. I need nothing to complete me,” Gilgamesh goaded him. “You’re just here to entertain me, got it? A pleasant evening where I get everything I want.”

He was trying to say something to make Rider give up, but the moment Rider was shirtless and tossing aside his sack, hat, cloak, and top, he gave up on the prissy attitude and opted for nothing but sheer thirst. If Arthur was built so fabulously beneath that armor of his, who could blame his other self for wanting to hoard him all to himself? And finally… one just for him…

“Will you be back next year?” A little too eager.

“Will you be good?”

It was hard to tell if this wasn’t just… Arthur, being put to the task of teasing Gilgamesh’s caster self, but those golden eyes were unmistakable. An Alter for sure, one with a cruel streak a mile wide if he was talking about being nice at a time like this.

“I’ll be good if you prove it’s worth it.”

Making a point of keeping his boots on, Arthur walked over to Caster and kissed him.

It was a warm, sultry kiss that Caster wanted to last for a bit longer than it did, but the promise of more was all the more enticing. If this really was an Arthur born from his wishes, then he’d know exactly what to do— pressing his knee up into his groin and letting his leather gloves wander his chest, pushing his vest off his shoulders and removing the circlet of horns from his head, all except for the jewel that sat in the middle of his hair. Caster relaxed in that moment, letting Arthur’s hand thread through his hair and tipping his head back for more kisses, as the other man worked his way down his neck and nibbled at his collarbone. He wasn’t necessarily touch-starved, but he was _hungry_ , and an appetite made of jealousy made him want to show this Santa off.

Unfortunately, before he could do much else, the hands that had been sitting at his side were taken and held close together, and quickly tied with what looked to be soft brown leather.

“… Ignorant mongrel, you know how easily I could break out of this—”

“But you won’t,” Alter whispered in his ear, Gilgamesh able to hear the smile on his lips. “Because you’d be breaking them without my permission, wouldn’t you?”

“… I see.” So that was the name of the game. Gilgamesh could easily use his strength to break such bonds, but Arthur was promising him it’d be much more pleasurable if he didn’t— so he wasn’t going to.

Arthur’s cool leather gloves touched the soft side of his stomach and made Gilgamesh bristle as he laid him back. More than accommodating him, Gilgamesh put his hands above his head and waited for Arthur to work that holiday magic.

He just didn’t expect Arthur, with those sharp new teeth, to be so bitey.

He worked bruises into his neck, biting his nape and licking the wound like a mark of pride. To be marked so insolently…! Still, it sent a sharp jolt of pleasure to his groin. He never imagined the sweet, noble Arthur to have a rough side, but these Alters were always something different… a little more mature, a little darker. He couldn’t deny that he loved the sensation.

“You’re beautiful…” Arthur whispered, not that Gilgamesh needed any flattery, but he could tell it came from a place of sincerity, which was always nice. He must share the same tastes as his Saber self. As Arthur’s hands roamed his body, Gilgamesh basked in the attention. Arthur was so dedicated, so attentive to the response of his body, from the sensitivity of his nipples to how he flinched when his lower abdomen was touched without warning. Arthur chuckled at that, knowing it was a sensitive spot on most people… but the King of Heroes, who didn’t allow people so close so often, having a place that made even him jolt— was very cute.

It was a shame he’d have to leave in the morning.

Arthur pulled their hips together and rocked them against Caster’s, letting him feel his length through the black pants he wore as part of his costume.

“How long has it been since you opened yourself to someone?” Arthur asked.

“Too long.”

“Then I will make this memorable.”

Alter unzipped his pants, but before pulling out any equipment, undid the red ties on Caster’s hips. He pulled the red pants off of him, before staring at the blue undergarment beneath, wondering how to deal with that. Gilgamesh laughed— even this Arthur had a cute side! He told Arthur how to remove it, and the man set about doing it. Now in nothing, he looked at Arthur, challenging him to do something interesting.

“Hmph,” A curt laugh from Arthur, before pushing down the front of his pants.

That’s… surely…

Did the original Arthur measure up to _that_?

No matter. With age, Gilgamesh was gifted talent, and the more he looked, the more excited he was to ride Arthur like a stallion, but the bonds on his wrists told him that Arthur would be in charge tonight— as long as Gilgamesh allowed it.

Arthur straddled his hips, frotting his cock against Gilgamesh’s, skin on skin filling the King with excitement. Arthur’s movements were slow and calculated, and Gilgamesh was judging him like he was on an Olympic panel. So far, he was a nine out of ten, but it’d take more than rubbing to get him off. Still… this was the hors d’oeuvres, the taste before the full meal. Arthur’s hands held the both of them together, stroking up and down as heat transferred between them.

“I wonder if you could be satisfied with something like this…”

“Never.”

“I thought not. Let’s try something.”

Arthur stood up and reached into his present bag to pull out a little golden box. Gilgamesh watched curiously as he opened it and removed its two contents— a vial of lubricant and a golden bullet vibrator. Arthur removed his gloves, finally.

“Modern-day technology… so crass.”

“I think you’ll enjoy it.” Arthur sat on the bed and slicked his fingers with lube, coating the toy in it and reaching between Gilgamesh’s legs, who involuntarily clenched down on his hand. As Arthur got him to relax, he pushed a single digit in as Caster moaned— a touch he’d dreamed of finally being realized. Arthur was doing such a thorough job too, stretching him out, scissoring him gently, adding a second and third finger to make sure he could take what was to come.

And then came the little vibrator.

To say he underestimated the sensation of something so new was an understatement.

It was such an inconspicuous thing, no more than a few inches long, but the rumble within him almost immediately forced an orgasm out of him, but he refused to let himself look weak in front of Arthur, who was wearing a smug smirk.

“I want you to let it all go,” Arthur said, quietly. “Don’t hold back, toss aside your pride for one moment.”

As Arthur turned the dial up, his head bobbed low and kissed the head of Gilgamesh’s dick. Gently sucking on the tip, his tongue swirled around it, thoroughly tasting him without shame. With one hand on the dial of the vibrator, he took the base of the cock into his hands and started to work on him with vigor. Gilgamesh could hardly stand it, arms going above his head involuntarily, making sure not to break his bonds but by the gods, was this Arthur talented. Each suck, each noisy motion that he almost felt was noisy on purpose was deliriously good, as if he was trying to drive his orgasm out from the inside and outside at the same time. He was utterly shameless, where he might picture a blush on Arthur’s face as Archer crooned and gripped his hair doing the same thing.

Let go. Toss away your pride.

He could never.

But his hips did eventually start rocking up into Arthur’s mouth, panting and moaning like it was the end of the world and Arthur was trying to save it. He felt like a dog, being dragged so low, but as the vibrator’s dial kept turning up, he wondered how long he could hold out. He might have more experience, but there was only so much one could do until—

Arthur took him down to the base, and Gilgamesh finally threw his pride out the window.

He came in Arthur’s throat, saliva pooling in his mouth and dripping out the corner of it, all as Arthur patiently kept his nose to his golden pubic hair and swallowed it all. That’s one way of not dealing with the taste, Gilgamesh thought— but while he thought the first orgasm of the evening was behind them, Arthur refused to take out the vibrator.

“Let’s keep you on edge,” He purred. “It’ll make this more fun.”

“I want to do something for you, too.”

The very obvious erection on Arthur looked too neglected to ignore, but Arthur did just that. “It isn’t about me, tonight. All of this is for you.”

Gilgamesh was used to being spoiled, but he wanted to do something for this Arthur while he was still materialized… no matter. As long as Arthur was calling the shots, he’d get everything he wanted and more. The vibration deep inside of him was already sending waves of pleasure up his spine, he had to wonder what Arthur planned next.

It was rope.

Someone must have put it on Gilgamesh’s Christmas list that he had a fondness for bondage, because Arthur knew all the right knots to tie so that this time, he really couldn’t break out of them. Well— he could, but he liked the struggle against them, and he wanted revenge with his chains, but turning the tables on Arthur would have to wait. Here he was, kissing his wrist as it started to rub against the rope.

“At least you’ll have some marks to remember me by,” Arthur said quietly, kissing the inside of Gilgamesh’s palm.

“You really can’t stay?”

“I’m born of a wish. It’s like Cinderella and the ball, by morning I’m gone.”

“Hm… then let’s make sure you enjoy this as much as I do.”

The only thing Gilgamesh could move were his legs, so he pressed the heel of his foot into Arthur’s groin. He stifled a moan, and it was so cute that Gilgamesh wanted more.

“You saw my weakness, now show me yours.”

“That’s all you’re going to get from me,” Arthur whispered back, moving to prop himself above Gilgamesh. “All I want is your pleasured expressions, your weak moans, your ecstasy… that is what I was born for. You are my weakness.”

How terribly romantic for someone who would disappear in the morning. Gilgamesh was starting to get annoyed at the fact that all the best things to happen to him eventually left him.

“Fuck me,” Gilgamesh ordered. “I want to get as much of you as I can before the night ends.”

Arthur could do nothing but oblige.

Spreading his legs, he poured the last of the lube onto his dick, rubbing it from top to bottom, coating it thoroughly before he pressed his way into Gilgamesh. Immediately, Gilgamesh understood why Arthur used this rope— he was weak to it somehow, some kind of resistance— he couldn’t break out of it if he tried, and he wanted to try. As he writhed in pleasure as Arthur pressed deeper into him, he wanted to hold him, so badly did he want to grip his shoulders and leave indents in his skin, to mark him up. Arthur was too pristine, let him mess him up a little!

But when all of Arthur’s cock was inside of him, thoughts like that went out the window. Arthur never took out the bullet vibrator, either. He merely drove it in deeper with his length, driving Gilgamesh ever closer to the brink. He struggled against his bonds, feeling himself harden again and so quickly— what was he even doing? Arthur told him to let go, so he tried doing just that— a deep sigh, throwing his head back on the pillow— all of it made the sensations sharper as Arthur thrust into him. Relaxing made everything a hundred times more intense, because he wasn’t focusing on what he wanted to do to Arthur.

He was just… getting what he wanted. What he so coveted his other self for.

“Cut the rope.” He ordered.

“Sorry, you look cute like this.”

“It was not a request.”

Gilgamesh’s Gate of Babylon opened behind him, a sharp blade protruding from it as Gilgamesh reached up and cut the ropes on it. Now freed, he reached up and gripped Arthur’s shoulders and dragged him down, down into a kiss that lasted several moments, parting to breathe and panting between breaths. He wanted this Arthur deeply, badly, he wanted to keep him like a toy for his stress and as a lover to boot— something curated for him so perfectly could not be let go of. Even if it was once a year, like some storybook fairytale— he would wait, damn it.

Arthur seemed surprised by his passion, surprised that he wanted to be so involved in his Christmas gift, but intuited that Gilgamesh was probably working out more than his frustrations on him at the moment. He kept his pace steady, not too fast or slow, making the moment last as long as he could, but eventually, Gilgamesh begged for more, rougher, harder— and he could do nothing but give it to him. Gripping his thighs and rutting into him so hard that other Chaldeans might hear it and not caring one bit, Arthur gave him everything he wanted.

Gilgamesh lost count of the times he came. First, it was in Arthur’s mouth, the second time was across his stomach— overstimulation was overwhelming, so much and so fast— Arthur didn’t come even once, even when Gilgamesh ordered him to release himself just as Arthur told him. It was as if he was solely focused on Gilgamesh’s pleasure, so much so that he had no time to focus on his own.

Gilgamesh eventually locked his legs around his waist, demanding that he wouldn’t let Arthur go until he came, and then, looking up into those amber eyes, he could see the toll it had taken on Arthur. Beads of sweat dripped down his face, his hands were shaking ever so slightly, enough for Gil to tell. As much as Arthur tried to argue, he couldn’t deny himself. He grabbed Gil’s hips and stilled his against him, coming inside of him and blessing the other man with a bit of his mana. As he pulled out, he finally took the bullet vibrator out too, but not before lowering himself to lick Gilgamesh’s torso, as if a single drop was not to be wasted.

If Gilgamesh didn’t just have the ride of his afterlife, he would have been hard again already. Just the sight of him… he truly was beautiful, and in Alter’s eyes, so was Gilgamesh.

“Are you done?” Gilgamesh asked, tentatively.

“Are you?”

“… no, never,” Gilgamesh smirked confidently, putting a hand to his lips. “You say you leave at dawn? Then you will fuck me until dawn, just as you have. Do you think I could be sated with just that? Hah! It’s as if you don’t even know me!”

Alter shut him up with a kiss, leaning in and tilting his head. Alter wouldn’t let him sleep a wink until he finally passed out, and while he listened to Arthur get dressed, he wanted to say something, his thanks, his goodbyes, his promise to see him again next year— but Arthur Alter was already gone, the door hadn’t even opened when he disappeared into the ether. Gilgamesh sighed, flopping on the bed, feeling like a mess.

“He better come back…”

—

As promised, Arthur Alter wasn’t anywhere during the next day in Chaldea.

He wasn’t sure why he got his hopes up that maybe Master summoned him properly, but he was more a gift than a servant. Part of Gilgamesh wondered if it was all a dream, but the mess he had to clean up told him otherwise. As he opened his tablet and began work once more, Archer marched over to him.

“Mongrel, how dare you encroach on what’s mine—”

“What are you talking about?”

“I heard Arthur in your room last night!”

“It wasn’t your Arthur,” Caster said stiffly. “It was a Santa version of him. He was here just for me.”

“Then where’s Arthur? Hmm? The one night of the year I’m supposed to spend with him, and—”

Just then, Arthur heard his name and followed the sound to the source. “Gil, I’m so sorry— Master needed me for a late-night mission last night. I promise I’ll make up Christmas for you today. Oh— Caster…” Arthur glanced his way. “You look really refreshed. Like you finally got a good night’s sleep.”

“I did, as a matter of fact. Arthur, once you’re done with _that_ me, would you mind accompanying me on a walk? There’s something I’d like to talk to you about.”

Arthur laughed nervously, knowing his answer between the two Gils was like trying to choose between two spiteful gods. “It’ll have to be a lot later, I really do have to make it up to Gil—”

“Sure. Leave, now, I have work to do.”

As the two walked away, Caster busily looked through Chaldea’s computer base to try and find Santa Alter’s spirit origin. Nothing… what a shame, both that Chaldea’s defenses could be so easily breached by one servant, and that their master hadn’t even met him. Still… his feelings couldn’t be ignored. Next year, he’d drag him by the ear to Ritsuka and make him stay. He made a promise, after all.

Whenever Caster needed wisdom, though… Enkidu was the right person to go to.

—

“I’m not surprised, to be honest,” Enkidu said, walking with him through Chaldea’s hallways. “You’re a magnet for the unusual.”

“It’s just a matter of bringing him back. I will not be denied what I want.”

Enkidu laughed. “Not when you’ve had a taste of it like that?”

“Exactly.”

“Well… I’m sure he’ll be back. Then, you can show him off to me. Your own Arthur. You’ve been jealous for a while now, haven’t you?”

“Was it obvious?”

“Terribly, but I know you better than most.”

Gilgamesh smirked. “I was never known for subtlety, I suppose. Especially around you.”

“Well, there’s lots to do on Christmas Day in Chaldea. Let’s find something fun, yeah? Take your mind off of it.”

Gilgamesh nodded, glancing back to the door to his room as they passed it. Little did he know, Arthur Alter had left a gift for him on the bedside table. A little box— a familiar (but brand new) toy and a little note, which read “To tide you over until next year. A promise is a promise.”

When he discovered it later, all he could do was smile.

**Author's Note:**

> AHHH I'M SO LATE TO THE CHRISTMAS PARTY
> 
> But here's this, thank you so much Basy for commissioning me!! ;__;


End file.
